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For anything that isn't a car you're gonna want gears for the same reason electric drills have gears. Think of it like low range. "muh instant 0rpm torque" is

For anything that isn't a car you're gonna want gears for the same reason electric drills have gears. Think of it like low range. "muh instant 0rpm torque" is absolutely nothing compared to the inertia of a hired driver who doesn't care (or is just a novice) dumping the clutch. Building a transmission to handle electric motor loads isn't a particularly remarkable engineering challenge. (Though you can make any engineering exercise challenging if you add sufficient weight and budgetary constraints) Imagine a medium or heavier truck that's expected to both get a load moving at low speed and to cruise at 80. Putting anything near peak power through an electric motor at low speeds lets the magic smoke out in short order. Sure you can gear it down but then you have insane rpm at high speed and the wonderful engineering problem of getting that insanely overbuilt motor to not fling itself apart at those speed. A simple two speed transmission is a far more elegant solution. Especially since a transmission for an electric motor can be far simpler than one for an ICE. Letting the magic smoke out was a big problem in early EV conversions because power was low and consequently the vehicles available for conversion didn't have lots of good options for deep gearing.

gwbas1c 6y ago
I've done both. Clutch dumps require that you rev the engine up to high RPMs first. Instant torque is, well, instant. I suggest you try it before you make fun of it.
- throwaway0a5e 6y ago
  Oh I know that a clutch dump is a far less elegant way to get moving than having torque available at 0rpm but the former is far, far harder on things. The point I'm trying to make is that the people acting like electric motors are particularly hard on drive-line components are just wrong.
bdamm 6y ago
Avoiding overheat conditions is something the vehicle engineering needs to deal with. Teslas solve this problem with liquid cooling and the motor controllers use temperature sensors in the motor core to determine if the currents are too great for the cooling. So really, no issue. I expect the Tesla Semi will handle heavy loads at low speeds just fine. As for clutch dumping, I'll take electronic stability and traction control over the smell of burning clutch any day. Plus, the traction delivery is better in an EV; much less rotating mass means more rapid response and a better grip on the road.
- throwaway0a5e 6y ago
  And depending on how much performance "dealing with overheat" conditions necessitates leaving on the table a multi transmission might be their solution. Porsche is doing just that.
Animats 6y ago
<i>For anything that isn't a car you're gonna want gears for the same reason electric drills have gears. Think of it like low range.</i> Not with modern motor controls. For the last 20 years or so, most new locomotives have used 3-phase AC servo drive motors. It's striking to see one exerting enormous torque to get a train started, yet the Diesel engine generating the power is barely above idle. Also, no wheel spin. All the wheels can be synchronized electrically. This almost doubles the useful traction. Early Teslas had a two-speed transmission. It was a flop. The shock loads on gear shifting were too large and the transmissions wore out rapidly. Tesla had to replace all of them. The big advance was liquid-cooled motors. Finally a way to get rid of the excess heat fast enough that you could use full power at zero speed if desired.
- throwaway0a5e 6y ago
  Locomotives have a very different relationship with weight than road going vehicles do. Of course an economy car will have a single speed transmission but vehicles that need to put out peak power at both low speeds and high speed (e.g. the Taycan, and an F250) are going to benefit greatly from a way to optimize for multiple speed ranges.
  - XorNot 6y ago
    I doubt it. There's no reason to bother doing the research to add another mechanical component which can wear and fail early, when you can just put a more powerful electric motor in. That's the thing: the incentive structure has changed. The better use of time and research dollars is going to be just upgrading that motor till it's adequate. There's a logical cap on the maximum road speed you need to accomodate, so the problem is eventually "solved" in practical terms.
    - bluGill 6y ago
      We have already put the effort into making transmissions though. Not a lot off research dollars needs to go into the problem at this point. It might or might not be worth it, but transmissions that last as long as the car with no maintenance are common (oil changes are recommended, but few people do).

gwbas1c 6y ago

I've done both. Clutch dumps require that you rev the engine up to high RPMs first. Instant torque is, well, instant. I suggest you try it before you make fun of it.

throwaway0a5e 6y ago
Oh I know that a clutch dump is a far less elegant way to get moving than having torque available at 0rpm but the former is far, far harder on things. The point I'm trying to make is that the people acting like electric motors are particularly hard on drive-line components are just wrong.

bdamm 6y ago

Avoiding overheat conditions is something the vehicle engineering needs to deal with. Teslas solve this problem with liquid cooling and the motor controllers use temperature sensors in the motor core to determine if the currents are too great for the cooling. So really, no issue. I expect the Tesla Semi will handle heavy loads at low speeds just fine. As for clutch dumping, I'll take electronic stability and traction control over the smell of burning clutch any day. Plus, the traction delivery is better in an EV; much less rotating mass means more rapid response and a better grip on the road.

throwaway0a5e 6y ago
And depending on how much performance "dealing with overheat" conditions necessitates leaving on the table a multi transmission might be their solution. Porsche is doing just that.

Animats 6y ago

<i>For anything that isn't a car you're gonna want gears for the same reason electric drills have gears. Think of it like low range.</i> Not with modern motor controls. For the last 20 years or so, most new locomotives have used 3-phase AC servo drive motors. It's striking to see one exerting enormous torque to get a train started, yet the Diesel engine generating the power is barely above idle. Also, no wheel spin. All the wheels can be synchronized electrically. This almost doubles the useful traction. Early Teslas had a two-speed transmission. It was a flop. The shock loads on gear shifting were too large and the transmissions wore out rapidly. Tesla had to replace all of them. The big advance was liquid-cooled motors. Finally a way to get rid of the excess heat fast enough that you could use full power at zero speed if desired.

throwaway0a5e 6y ago
Locomotives have a very different relationship with weight than road going vehicles do. Of course an economy car will have a single speed transmission but vehicles that need to put out peak power at both low speeds and high speed (e.g. the Taycan, and an F250) are going to benefit greatly from a way to optimize for multiple speed ranges.
- XorNot 6y ago
  I doubt it. There's no reason to bother doing the research to add another mechanical component which can wear and fail early, when you can just put a more powerful electric motor in. That's the thing: the incentive structure has changed. The better use of time and research dollars is going to be just upgrading that motor till it's adequate. There's a logical cap on the maximum road speed you need to accomodate, so the problem is eventually "solved" in practical terms.
  - bluGill 6y ago
    We have already put the effort into making transmissions though. Not a lot off research dollars needs to go into the problem at this point. It might or might not be worth it, but transmissions that last as long as the car with no maintenance are common (oil changes are recommended, but few people do).